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POP particle collision/final resting

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OK... I think I've exhausted my button pushes and research. If anyone can give any pointers about getting my collisions/debris to actually appear to rest on the surface and/or interact with the moving model I would be very thankful. Currently, the `debris` appears to come to a final rest above the surface. I've included the scene and ref'd geo.


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hey there,

your pscale is way larger than your pieces. fixed it by using a matchsize scaling the popcorn to a 2,2,2 bounding box (since pscale = radius). visualizing this attribute as a vector helps a lot when troubleshooting.

another issue was the transform on "moon_terrain" obj -> you have to enable 'use object transform' on the terrainobject.

sleep delay was really low so particles would fall asleep mid air due to gravity slowing them down.

i dont think you're using the vdb out from the moon_terrain at all, but that network has duplicate nodes stacked on top of each other (eg. VDB1 null, collisionsource). the collisionsource also has a bad parameter reference resulting in a divsize of 0.


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Thank you so much for your detailed feedback. All of this info is very educational and are the tiny bits and pieces that add up to experience to be able to help others. The pscale problem, I'm not sure if I would have figured out. The `use object transform` I'm pretty sure I checked that on and off at some point and I played with the sleep delay a bit. The VDB I think was created from one of the shelf tools, so I'm not sure what I did there.

How did you determine the pscale was too big (aside from the geo not touching the terrain). Are there any values that tipped you off?


Again- Thank you.

Edited by quinniusmaximus

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hey! you can visualize attribute values in the viewport - eg. when you inspect a node (the info panel where you see point count, groups, etc..) simply click on the attribute name and houdini creates a scene visualizer for it. you can set up multiple visualizers and toggle them on and off via the visualizations menu (bottom right of the viewport, looks like a location marker) or the viewport display options. You can also make a local visualizer with the sop node (hotkey x).

if you visualize pscale as a marker with the vector style you see the radius of the particles. just compare the length of these vectors with the size of the instanced objects, its easy to spot. With particles pscale indicates the radius of the sphere used for collision detection, but when instancing the object pscale also is a multiplyer to the instances scale. So if the source object is not unit-size it will not match the collision object.

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